Better Roads

August 2013

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RoadScience
other, sometimes generating rancor.
What is not arguable is that LCCA is a process of selecting the most economical pavement design based on initial
construction costs and future maintenance, rehabilitation and
reconstruction costs.
LCCA is a process for evaluating transportation project
expenditures. "LCCA will assist in determining the best – the
lowest-cost – way to accomplish the project," says FHWA's
Life Cycle Cost Analysis Primer (2002). The five steps to LCCA, according to the primer, are
• Establish design alternatives.
• Determine activity timing.
• Estimate costs (agency and user).
• Compute life cycle-costs, and
• Analyze the results.
Significantly, best-practice LCCA calls for including not
only direct agency expenditures (for example, construction
or maintenance activities), but also costs to facility users that
result from these agency activities.
"The predicted schedule of activities and their associated agency and user costs form the projected life-cycle
cost (LCC) stream for each design alternative," FHWA says.
"Using an economic technique known as 'discounting,' these
costs are converted into present dollars and summed for each
alternative. The analyst can then determine which alternative
is the most cost-effective."
FHWA notes the lowest LCC option may not necessarily be
implemented when other considerations such as risk, available budgets, and political and environmental concerns are
taken into account, adding "LCCA provides critical information to the overall decision-making process, but not the final
answer."
Although LCCA was only officially mandated in a very
limited number of situations, FHWA has always encouraged
the use of LCCA in analyzing all major investment decisions
where they are likely to increase efficiency and effectiveness.
However, the 1998 Transportation Equity Act for the 21st Century
(TEA-21) removed the requirement for state highway agencies to conduct LCCA on high-cost NHS useable project
segments.
But the philosophy lives on. A 2011 National Cooperative
Highway Research Program project – NCHRP No. 703: Guide
for Pavement Type Selection (Google NCHRP No. 703) – surveyed
state transportation agencies and reported that 29 of 35 states
that responded use LCCA for new construction or reconstruction projects.
Because there is no current requirement that LCCA be
conducted or used to select among pavement types used on
federally funded highway projects, federal LCCA guidance
and assistance to state transportation agencies is advisory.
Beginning in August 2012 – in an effort to shine a light
on a process that could cause federal funds to be spent more
wisely, and to fulfill a mandate of MAP-21 – the Government
Accountability Office (GAO) looked closely at use of LCCA
among the states.
The result is the June 2013 report, Improved Guidance Could
Enhance States' Use of Life-Cycle Cost Analysis in Pavement Selection
(Google GAO-13-544). GAO visited four states to interview
local FHWA, state DOT and asphalt and concrete pavement
industry association representatives, and conducted telephone interviews with state transportation agency officials
in 12 more states. Selection criteria includes a wide range of
LCCA approaches and a wide geographical distribution of
states.
GAO found a mixed bag, with no great lessons to learn.
"Information gathered from these states is not generalizable
to all states," GAO reports. "States' life-cycle cost analysis
practices vary, though they are often informed by FHWA
guidance. Most of the selected states we reviewed use LCCA
in some capacity to help ensure the long-term cost-effectiveness of investment decisions.
"Thirteen of 16 states included in our review used it in
some capacity," GAO says. "State transportation officials in
[those] 13 states indicated that the goal of LCCA was to help
ensure that the agency makes long-term, cost-effective investment decisions. Some state officials also noted that LCCA
could help the state transportation agency communicate to
stakeholders – pavement industry representatives, state legislators, and taxpayers – that it is making sound decisions."
Mechanistic-Empirical Design
Even as LCCA evolves, with a strong shove by AASHTO, the
"hands on" mechanistic-empirical design philosophy is taking root in road agencies from coast to coast.
The Mechanistic-Empirical Pavement Design Guide, Interim Edition: A
Manual of Practice provides more reliable pavement designs for
all pavement types, based on in-service conditions, according to ARA, creator of the MEPDG. The guide and associated
software – now in various stages of adoption throughout
the state DOTs – provide a state-of-practice mechanisticempirical highway pavement design methodology based on
actual experience from the real world, translated to a design
program (see "To Prevent Failure, Begin with Better Bases," May
2013, pp. 20-27).
Pavement ME Design is the next generation of AASHTOWare pavement design software, which builds upon the
mechanistic-empirical pavement design guide, and expands
and improves the features in the accompanying prototype
computational software.
Using real-world conditions, the MEPDG represents a
major change in the way pavement design will be performed, and in a way, is not unlike of the Superpave system
of performance-based mix design specs.
Mechanistic-empirical are big words that describe a very
simple concept. "Mechanistic" refers to the interaction
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